1. Field of the Invention
The present invention generally relates to a safety feature that has a locking device or system to prevent unauthorized movement of a shift mechanism in a vehicle, such as an automobile.
2. Description of Related Art
Regulatory requirements mandate various vehicle safety features for the prevention of inadvertent and/or unintended vehicle movement and/or acceleration, regardless of whether a vehicle key is in or out of an ignition and regardless of a key position in the ignition. These safety features are intended to prevent movement of a transmission shift mechanism in order to prevent accidents resulting from vehicles accidentally or unintentionally rolling away or accelerating. Two types of current safety features are known as park-lock systems, which are intended for situations where the key is not in the ignition, and brake transmission shift interlocks (BTSI) systems, which are intended for situations where the key is in the ignition.
Park-lock systems engage the shift mechanism and prevent movement of the shift mechanism until a key is placed within a key cylinder in a traditional system, or a wireless transmitter activates a wireless receiver in a keyless ignition system. When utilized in an automatic transmission, the park-lock system locks the shift mechanism in a park position. Although these park-lock systems are effective, they do not address the safety feature of unauthorized movement of the shift mechanism through an entire range of potential situations.
BTSI systems interconnect the shift mechanism to a brake pedal of the vehicle such that a driver cannot move the shift mechanism until the brake pedal is depressed. Typically in an automatic transmission, the driver cannot move the shift mechanism from the park position until the brake is depressed. These BTSI systems are effective to prevent unwanted vehicle acceleration, but are not designed to be functional throughout an entire range of all positions of the ignition system. In other words, BTSI systems are primarily activated/engaged only when a vehicle engine is running. Other positions of the ignition system include stop, one or more accessory, and start positions. Some BTSI systems have been converted to be activated/engaged during an accessory position but become de-activated during transitions between the other states of the ignition system.
One contemplated solution is to reverse the BTSI system such that the BTSI system is continuously engaged and is then deactivated when the driver depresses the brake pedal. However, to accomplish this solution would require a completely new design and also presents a potential safety hazard. In particular, if the vehicle was to loose power during operation, the BTSI system would re-engage and lock the shift mechanism thereby creating an undesirable situation. To overcome this safety issue, the reversed BTSI design would require a mechanical override, which provides an added cost. The override would also be required to move the vehicle during the assembly process prior to battery power connection.
Accordingly, it is desirable to develop a safety system that prevents unauthorized movement of the shift mechanism in all potential safety situations while avoiding the limitations of the prior art.